The purpose of this supplement is to explore two possible genetic influences, the serotonin transporter (5-HTT) gene and the dopamine D4 receptor (DRD4) gene, on sexual risk behavior and STD incidence among young expectant parents. We will incorporate biological influences within a larger ecological framework to assess how genetic and biological factors interact with psychological, social, and environmental factors to influence sexual risk and STD incidence among young couples. We will examine these issues in a sub-study of a multi-site longitudinal study of young expectant fathers and their pregnant adolescent partners. The sub-study will assess 432 men and women to be conducted in health clinics in Connecticut. Data will be collected through Audio Computer Assisted Self-Interview (ACASI), semi-annual STD testing, and genetic testing through buccal swabs. Members of a couple will be assessed at three time points regardless of relationship status: during 3rd trimester of pregnancy, 6-months postpartum, and 12 months postpartum. The aims of the study are to describe the frequencies of 5-HTTLPR and DRD4 genetic polymorphisms among low-socioeconomic status, mostly minority young couples transitioning to parenthood, and to assess the interactions between 5-HTTLPR and DRD4 genetic polymorphisms and dyadic, family, and community-level psychosocial factors on sexual risk behavior and STD incidence. Genetic and environment interactions have been shown to play an important role in other risk behaviors among youth. Therefore, identifying possible genetic-environmental interactions in high- risk populations may aid in the creation of tailored interventions that have the best success to lead to long-term behavioral change. The goal of this supplement is to be one of the first studies to explore possible genetic and psychosocial interactions on HIV/STD risk behavior among young heterosexual couples and to use these results to design larger cohort and intervention studies that assess genetic-psychosocial-behavioral interactions. PUBLIC HEALTH RELEVANCE: This study will assess how genetic and biological factors interact with psychological, social, and environmental factors to influence sexual risk and STD incidence among young couples. Results can be used to inform and tailor prevention interventions aimed at reducing HIV and STDs among men, women, and couples. [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable]